modeling wireless power transfer

www.ozeninc.com info@ozeninc.com (408) 732 4665 1210 E Arques Ave St 207 Sunnyvale, CA 94085

Reliable World Class Insights

Your Silicon Valley Partner in Simulation

ANSYS Sales, Consulting, Training & Support

© 2012 ANSYS, Inc. December 18, 20141

Modeling Wireless Power Transfer in ANSYS

© 2012 ANSYS, Inc. December 18, 20142

Physical domains and systems

Thermal domain

Electromagnetic domain

Fluid Flow domain

Mechanical domain

© 2012 ANSYS, Inc. December 18, 20143

Physical domains and systems

Transmitter coil sub-system

Control

Power supply

Circuit

Receiver coil sub-system

Load Circuit

© 2012 ANSYS, Inc. December 18, 20144

Geometry

© 2012 ANSYS, Inc. December 18, 20145

Near-Field (Inductive coupling, resonant) • Not based on propagating EM waves• Operates at distances less than a wavelength of

transmission signal• Resonance obtained by use of external circuit capacitor• Typical challenges include: coil size, shape, number of

turns, saturation, self and mutual inductance, AC resistance, frequency response, losses, efficiency

Far-Field (resonant)• Microwave Type• Operating range to ~10 meters• Tradeoff between directionality and transmission

efficiency• Self capacitance of coil turns is of importance

Wireless Power Transfer

© 2012 ANSYS, Inc. December 18, 20146

Method Map

1mm 1cm 10cm 1m 10m 100m

100%

50%

0%

Transfer Distance

Effic

ienc

y

Resonance type

Induction type (~15W) Induction type (~50kW)

Microwave type

Ref.：EE Times Japan 2009.10

© 2012 ANSYS, Inc. December 18, 20147

1mm 1cm 10cm 1m 10m 100m

100%

50%

0%

Transfer Distance

Effic

ienc

y

Resonance type

Induction type (~15W) Induction type (~50kW)

Microwave type

ANSYS Solution for each WPT type

HFSSDesigner

MaxwellSimplorer

Ref.：EE Times Japan 2009.10

© 2011 ANSYS, Inc. December 18, 2014

8

Large Gap Transformer Design Using Computational Electromagnetics (CEM)

© 2011 ANSYS, Inc. December 18, 2014

9

• Low reluctance flux path is available

• Mutual Coupling between the coils can be easily determined using Magnetic Circuit approach

• Leakage flux can be considered to be negligible

• Mutual inductance can be derived using flux balance

• Analytical solution possible within permissible level of accuracy

Transformer

© 2011 ANSYS, Inc. December 18, 2014

10

• No Specific path for the magnetic flux

• Leakage flux is significant enough and can not be neglected

• Analytical methods are proposed for calculation of Mutual inductance using Maxwell’s formula for two coaxial circular coils

Large Gap Transformer

𝑴𝑴 =𝟐𝟐𝝁𝝁𝟎𝟎 𝑹𝑹𝒑𝒑𝑹𝑹𝒔𝒔

𝒌𝒌𝟏𝟏 − 𝒌𝒌𝟐𝟐

𝟐𝟐𝑲𝑲 𝒌𝒌 − 𝑬𝑬 𝒌𝒌

𝑲𝑲 𝒌𝒌 ,𝑬𝑬 𝒌𝒌 are elliptical integrals of first and second kind

Application of these formulas to real life cases is almost impossible

Computation Electromagnetics can help to reduce problem complexity significantly - Maxwell

© 2011 ANSYS, Inc. December 18, 2014

11

Maxwell

© 2011 ANSYS, Inc. December 18, 2014

12

• Easy-to-use GUI• Features entered through GUI• Fast Learning Curve• Integrated under ANSYS Workbench (WB)

Graphical User Interface (GUI)

© 2011 ANSYS, Inc. December 18, 2014

13

Measured

Automatic Adaptive Meshing

© 2011 ANSYS, Inc. December 18, 2014

14

• Allows any arbitrary mathematical manipulation of basic field quantities• Allows to easily define any post-processing quantity

Fields Calculator

© 2011 ANSYS, Inc. December 18, 2014

15

• Flexible and easy-to-use post-processing capabilities• Field plots can be generated in volumes, on surfaces and on any defined planes. Mesh,

magnitude, vector and streamline plots of basic field quantities are readily available

Post Processing

© 2011 ANSYS, Inc. December 18, 2014

16

• Arbitrary time-dependent voltage and current excitations to drive the coils• Measured waveform can be imported to be used as a coil excitation• Maxwell is capable of modeling translational, rotational cylindrical and rotational non-cylindrical

(relay type) motion• Equation of Motion can be considered

Time domain analysis with motion

© 2012 ANSYS, Inc. December 18, 201417

Inductive Type Coupling – Near Field

1) Electromagnetic analysis to determine R, L, M

Magnetic → R, L, MR

C C

R

LLM

2) Resonant circuit realized by a lumped capacitance parameter in the circuit simulator

© 2012 ANSYS, Inc. December 18, 201418

Example

20kW @ 400V/20kHz

Core

CoilShield Plate

Secondary Coil

Primary Coil

© 2012 ANSYS, Inc. December 18, 201419

Solution Flow Chart

MagnetostaticAnalysis

Frequency domainAnalysis Circuit Analysis

AC / TRState-Space Model

Circuit / Drive / Controller designWaveform, Efficiency, Power factor, Response

Frequency domainAnalysis

Field, Loss

Core, Winding

GapSliding

© 2012 ANSYS, Inc. December 18, 201420

• A Static Magnetic analysis using ANSYS Maxwell can calculate the self as well as mutual inductances of such a system

• Coils can be modelled as a lumped objects to reduce the simulation complexity

Magnetostatic Analysis using Maxwell

L1 MM L2

© 2012 ANSYS, Inc. December 18, 201421

Flux Density Distribution

© 2012 ANSYS, Inc. December 18, 201422

0.00 100.00 200.00 300.00 400.00H (A_per_meter)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

B (t

esla

)

Magnetostatic Analysis using Maxwell

Verification for core saturation– Core’s BH curve, Mag_B field plot– No magnetic saturation

Nonlinear BH curve 0.00 20.00 40.00 60.00 80.00 100.00Current [A]

0.00

0.01

0.10

1.00

Gap

[met

er]

2D_Static_BHMutual Inductance L12 ANSOFT

Matrix1.L(C [nH]

0.0000e+000

5.7000e+003

1.1400e+004

1.7100e+004

2.2800e+004

2.8500e+004

3.4200e+004

Specification Area

As Maximum Flux Density is within linear region, cores can be modelled as Linear magnetic material

© 2011 ANSYS, Inc. December 18, 2014

23

Parametric Analysis

• In Example, we assumed that spacing between the coils is fixed and axis of the sender and receiver is perfectly aligned

• In Practice,– Distance between the coils can vary significantly – Misalignments in coil axis can also be present

• Analysis needs to be performed to determine magnetic coupling between two coils as function of the spatial location with respect to each other

© 2011 ANSYS, Inc. December 18, 2014

24

Parametric Analysis using Maxwell

© 2011 ANSYS, Inc. December 18, 2014

25

Parametric Analysis using Maxwell

© 2011 ANSYS, Inc. December 18, 2014

26

Parametric Analysis using Maxwell

Mutual Inductance Vs Gap Vs Slide

Coupling Coefficient Vs Gap Vs Slide

© 2012 ANSYS, Inc. December 18, 201427

Eddy Current (Frequency domain)• Impedance vs frequency

• State Space Model for Circuit Analysis

• Losses

• Eddy current shielding

Shield Plate (Aluminum)

Core(Power Ferrite)

© 2011 ANSYS, Inc. December 18, 2014

28

Loss CalculationSpecifying Eddy Current Calculations in Shields

Define Electrical Conductivity for the shields in Siemens/mShields are modelled as Aluminum in this example and are specified with Conductivity of Aluminum

Turn ON the eddy current calculation for the shield objects

© 2011 ANSYS, Inc. December 18, 2014

29

Loss CalculationSpecifying Core Loss Calculations in Core Plates

Input Core Loss vs Frequency data for the range of frequencies that you wish to operate onCore Loss Coefficients are calculated automatically

Turn ON Core Loss calculation for the cores

© 2011 ANSYS, Inc. December 18, 2014

30

Loss CalculationCore Losses in the Core Plates at 100 kHz

© 2011 ANSYS, Inc. December 18, 2014

31

• Once the Large Gap Transformer is analyzed in isolation, it needs to be included in a system level simulation

• The model of the transformer represented on system level should include the accurate representation as simulated using CEM

• A state space representation can be extracted from CEM model by defining a frequency sweep

• A frequency sweep will also help in analyzing system performance to frequency deviations

Frequency Sweep

© 2011 ANSYS, Inc. December 18, 2014

32

Frequency Sweep

Core Loss Vs Frequency

© 2011 ANSYS, Inc. December 18, 2014

33

Large Gap Transformer Design Using Computational Electromagnetics (CEM)

© 2012 ANSYS, Inc. December 18, 201434

0 0

R1

(1/87) ohm

R2

(1/348) ohm

L1

0.19267mH

L2

0.048166mH

M1

0.5668

Cs

1.93uF

Cp

5.24uF

Rload

10ohm

W+

WM1

W+

WM2

E1AMPL=200VFREQ=10kHz

Coupling Simulation EM and Circuit

0 0

R1

(1/87-0.004) ohm

R2

(1/348-0.001) ohm

Cs

1.87uF

Cp

5.23uF

Rload

10ohm

W+

WM1

W+

WM2

E1AMPL=200VFREQ=10kHz

Current_1st_1:src

Current_1st_2:src

Current_2nd_1:src

Current_2nd_2:src

Current_1st_1:snk

Current_1st_2:snk

Current_2nd_1:snk

Current_2nd_2:snk

＝

AC / Frequency domain TR / Time domain

Model Generated by Field Simulator

© 2012 ANSYS, Inc. December 18, 201435

Circuit Design: Resonance Capacitor type

SS, SP, PS, PP type

Ref.: ANSYS Automotive Seminar, 30.Oct.2012, “Design of A Zero-Voltage-Switching Large-Air-Gap Wireless Charger for Plug-in Hybrid Electric Vehicles”. Kevin (Hua) Bai, Department of Electrical and Computer Engineering, Kettering University

© 2012 ANSYS, Inc. December 18, 201436

0

0

0

R1

7.2mOhm

R2

3.6mOhm

Cs

1.72uF

Cp

4.96uF

Rload

13ohm

W

+WM1

W

+WM2

D4

D3

D2

D1

IGBT4

IGBT3

IGBT2

IGBT1

C1

1000uF

TRANS4

DT4

TRANS3

SINE1.VAL > TRIANG1.VAL

TRANS2

DT1

TRANS1

SINE1.VAL < TRIANG1.VAL

STATE_11_4

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0SET: TSV1:=0DEL: DT4##Dead_Time

STATE_11_3

SET: TSV4:=0SET: TSV3:=1SET: TSV2:=1SET: TSV1:=0

STATE_11_2

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0SET: TSV1:=0DEL: DT1##Dead_Time

STATE_11_1

SET: TSV4:=1SET: TSV3:=0SET: TSV2:=0SET: TSV1:=1

TRIANG1

AMPL=1FREQ=Carrier_Freq

SINE1

AMPL=Modulation_IndexFREQ=Frequency

ICA: FML_INIT1

Modulation_Index:=0Carrier_Freq:=20kFrequency:=20k

DC_Source:=400Dead_Time:=2u

~

3PHAS

~

~

A * sin (2 * pi * f * t + PHI + phi_u)

PHI = 0°

PHI = -120°

PHI = -240°

THREE_PHASE1D5

D6

D7

D8

D9

D10 Battery- +

LBATT_A1

D11

D12

D13

D14

C2

1uF

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-150.00

-100.00

-50.00

0.00

50.00

100.00

150.00

Y1

[A]

Curve Info rmsWM1.I

TR 41.6165

WM2.ITR 34.8648

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-800.00

-300.00

200.00

700.00

Y1

[V]

Curve Info rmsWM1.V

TR 281.0066

WM2.VTR 321.9453

2.900 2.925 2.950 2.975 3.000Time [ms]

-250.00

-125.00

0.00

125.00

250.00

Y1

[A]

-1000.00

-500.00

0.00

500.00

873.02

Y2

[V]

MX1: 2.9200MX2: 2.9811

-408.7847-315.0105-64.8250

-40.2840-377.1247-319.5653 -53.6971

-0.0037

0.0610

Curve Info Y Axis rmsWM1.I

TR Y1 38.9542

WM2.ITR Y1 34.1140

WM1.VTR Y2 276.0822

WM2.VTR Y2 316.6292

PWRProbe

PWR_Probe1

Current_1:srcCurrent_2:src

Current_1:snkCurrent_2:snk

PWRProbe

PWR_Probe2

System Simulation

AC400V Rectify InverterWireless Power Transformer Battery

Controller

© 2012 ANSYS, Inc. December 18, 201437

Efficiency Map

Output/Input Power

Tuned capacitance for each condition

90%

50%

20%

[%]100

cos

×=

=

in

out

PPVIP

η

θ

Effic

ienc

y[%

]

Sliding [mm]Gap [mm]

Gap Sliding

Max.96%

© 2011 ANSYS, Inc.38

Efficiency as a function of sliding direction and distance

• Gap between coils kept constant

© 2011 ANSYS, Inc.39

Efficiency as a function of gap between coils

• Zero sliding

Gap

© 2012 ANSYS, Inc. December 18, 201440

Field solution using the currents from the circuit simulation

Magnetic Field Intensity Magnetic Flux Density

0.00 0.20 0.40 0.60 0.80 1.00Distance [meter]

0.00

0.00

0.01

0.10

1.00

10.00

Mag

_B [m

Tesl

a]2D_EddyXY Plot 1 ANSOFT

Curve InfoMag_B

Setup1 : LastAdaptiveFreq='20kHz' Phase='0deg'

Distance

Distance

© 2012 ANSYS, Inc. December 18, 201441

Field solution using the currents from the circuit simulation

Core Losses Shield Losses

Primary

Secondary

© 2012 ANSYS, Inc. December 18, 201442

Summary

ANSYS offers a comprehensive modeling solution for Wireless Power Transfer systems:

– Magnetostatic – Frequency domain– Circuit and system level– Multiphysics

Wireless Power TransferElectromagnetics

System Level ModelingElectromagnetic-Circuit

0

0

0

R1

7.2mOhm

R2

3.6mOhm

Cs

1.72uF

Cp

4.96uF

Rload

13ohm

W

+WM1

W

+WM2

D4

D3

D2

D1

IGBT4

IGBT3

IGBT2

IGBT1

C1

1000uF

TRANS4

DT4

TRANS3

SINE1.VAL > TRIANG1.VAL

TRANS2

DT1

TRANS1

SINE1.VAL < TRIANG1.VAL

STATE_11_4

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0SET: TSV1:=0DEL: DT4##Dead_Time

STATE_11_3

SET: TSV4:=0SET: TSV3:=1SET: TSV2:=1SET: TSV1:=0

STATE_11_2

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0SET: TSV1:=0DEL: DT1##Dead_Time

STATE_11_1

SET: TSV4:=1SET: TSV3:=0SET: TSV2:=0SET: TSV1:=1

TRIANG1

AMPL=1FREQ=Carrier_Freq

SINE1

AMPL=Modulation_IndexFREQ=Frequency

ICA: FML_INIT1

Modulation_Index:=0Carrier_Freq:=20kFrequency:=20k

DC_Source:=400Dead_Time:=2u

~

3PHAS

~

~

A * sin (2 * pi * f * t + PHI + phi_u)

PHI = 0°

PHI = -120°

PHI = -240°

THREE_PHASE1D5

D6

D7

D8

D9

D10 Battery- +

LBATT_A1

D11

D12

D13

D14

C2

1uF

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-150.00

-100.00

-50.00

0.00

50.00

100.00

150.00

Y1

[A]

Curve Info rmsWM1.I

TR 41.6165

WM2.ITR 34.8648

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-800.00

-300.00

200.00

700.00

Y1

[V]

Curve Info rmsWM1.V

TR 281.0066

WM2.VTR 321.9453

2.900 2.925 2.950 2.975 3.000Time [ms]

-250.00

-125.00

0.00

125.00

250.00

Y1

[A]

-1000.00

-500.00

0.00

500.00

873.02

Y2

[V]

MX1: 2.9200MX2: 2.9811

-408.7847-315.0105-64.8250

-40.2840-377.1247-319.5653 -53.6971

-0.0037

0.0610

Curve Info Y Axis rmsWM1.I

TR Y1 38.9542

WM2.ITR Y1 34.1140

WM1.VTR Y2 276.0822

WM2.VTR Y2 316.6292

PWRProbe

PWR_Probe1

Current_1:srcCurrent_2:src

Current_1:snkCurrent_2:snk

PWRProbe

PWR_Probe2